聚乙烯绝缘中温度梯度效应对直流电场的畸变特性

Temperature Gradient Effect on Distortion of DC Electrical Field in Polyethylene

针对直流电缆内外温差与直流电场共同作用下会影响绝缘材料内部空间电荷分布和电场分布的问题,利用自行研制的温度梯度下的空间电荷测量装置,通过设定不同的上、下电极温度,实现试样上、下表面的不同温差,然后采用阶梯升压方式(10、30、50、70MV/m),测量在不同温度差(ΔT为0～40℃)下聚乙烯中的电场分布,最后得出了温度差和电场分布的关系.结果表明:温度差越大,外施场强越高,试样体内低温侧场强畸变越严重;由于高场强下电极上同极性电荷的注入,加压时间的增加对畸变场强有一定的缓和作用.

Space charge profiles and stress distributions in cable bulk are strongly affected by high voltage direct current （HVDC） voltage, especially with the cooperation of the temperature difference between inner and outer insulations. A modified space charge measurement system suitable for temperature gradient was designed to fulfill the temperature difference via changing the upper and lower electrode temperature. Then space charge profiles and stress distributions in low density polyethylene （LDPE） were measured under different temperature differences （from 0℃ to 40 ℃）, as applied DC stresses of 10, 30, 50, and 70 MV/m, respectively. The relationship between temperature difference and stress distribution was obtained. The test results show that the increasing temperature difference and applied stress results in a more distorted stress at the low temperature site of sample. And due to the injection of homo-charges from the electrode under high electrical stress, the distorted stress is reduced with the increasing poling time.